40mm cylinder or 44mm cylinder for my 49cc bike motor

[Greg58]

What's your take on the 49mm bore cylinder kits? I love them! Makes ample power for me.

Mine runs great in the upper rpm range but not at lower rpm's, I opened up the ports a little much. I added the expansion chamber and it helped some with low end. I have another cylinder that i can give a second try to get better overall performance.